Performing authentication

ABSTRACT

Preference data is received. The received preference data is compared to stored preference data associated with a user with which the received preference data is associated. A determination is made whether to authorize an action based at least on the comparison. The preference data is received as a selection.

CROSS REFERENCE TO OTHER APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 12/215,048, entitled PERFORMING AUTHENTICATION filed Jun. 23,2008, which is a continuation-in-part of U.S. patent application Ser.No. 11/890,408, entitled METHOD AND APPARATUS FOR EVALUATING ACTIONSPERFORMED ON A CLIENT DEVICE filed Aug. 6, 2007, which claims priorityto U.S. Provisional Application No. 60/836,641, entitled METHOD ANDAPPARATUS FOR IMPROVED WEB SECURITY filed Aug. 9, 2006, and claimspriority to U.S. Provisional Application No. 60/918,781, entitled SECURELOGGING OF CRITICAL EVENTS, ALLOWING EXTERNAL MONITORING filed Mar. 19,2007, all of which are incorporated herein by reference for allpurposes. U.S. patent application Ser. No. 12/215,048 also claimspriority to U.S. Provisional Patent Application No. 60/967,675, entitledMethod AND APPARATUS FOR LIGHT-WEIGHT AUTHENTICATION filed Sep. 6, 2007,which is incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

Authentication techniques are used to ensure that actions, for exampleaccessing a computer or other resource, are performed only by anauthorized human or other user. One way that websites and otherelectronic services authenticate their users is by requiring those usersto supply a username and a valid password before being granted access.Typically the password is selected by the user the first time the uservisits the site (e.g., as part of a registration process), and may bechanged by the user as desired. Unfortunately, users sometimes forgettheir passwords—especially if the password is complex or usedinfrequently. Passwords can also be difficult to type, for example ifthe user is using a client with limited input capabilities.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are disclosed in the followingdetailed description and the accompanying drawings.

FIG. 1 illustrates an embodiment of an environment in whichauthentication is provided.

FIG. 2 is a flow chart illustrating an embodiment of an enrollmentprocess.

FIG. 3A illustrates an embodiment of an interface for capturingpreference information.

FIG. 3B illustrates an embodiment of an interface for capturingpreference information.

FIG. 3C illustrates an embodiment of an interface for capturingpreference information.

FIG. 4 illustrates an embodiment of an interface for capturingpreference information.

FIG. 5 is a flow chart illustrating an embodiment of an authenticationprocess.

FIG. 6 illustrates an embodiment of an interface for authenticating auser.

DETAILED DESCRIPTION

The invention can be implemented in numerous ways, including as aprocess; an apparatus; a system; a composition of matter; a computerprogram product embodied on a computer readable storage medium; and/or aprocessor, such as a processor configured to execute instructions storedon and/or provided by a memory coupled to the processor. In thisspecification, these implementations, or any other form that theinvention may take, may be referred to as techniques. In general, theorder of the steps of disclosed processes may be altered within thescope of the invention. Unless stated otherwise, a component such as aprocessor or a memory described as being configured to perform a taskmay be implemented as a general component that is temporarily configuredto perform the task at a given time or a specific component that ismanufactured to perform the task. As used herein, the term ‘processor’refers to one or more devices, circuits, and/or processing coresconfigured to process data, such as computer program instructions.

A detailed description of one or more embodiments of the invention isprovided below along with accompanying figures that illustrate theprinciples of the invention. The invention is described in connectionwith such embodiments, but the invention is not limited to anyembodiment. The scope of the invention is limited only by the claims andthe invention encompasses numerous alternatives, modifications andequivalents. Numerous specific details are set forth in the followingdescription in order to provide a thorough understanding of theinvention. These details are provided for the purpose of example and theinvention may be practiced according to the claims without some or allof these specific details. For the purpose of clarity, technicalmaterial that is known in the technical fields related to the inventionhas not been described in detail so that the invention is notunnecessarily obscured.

Those who control access to computer or other resources commonly useautomated techniques to verify the identity of a person or other userattempting to take an action with respect to the resource, such asaccessing account or other information, performing an operation, etc.For example, if a user is unable to remember his or her password, thatuser typically can request that the password be reset via an automatedprocess by which the identity of the user is attempted to be verified.Assorted schemes exist that attempt to determine whether a particularreset request has been submitted by a legitimate user that has genuinelyforgotten his or her password or by a nefarious individual attempting togain unauthorized access to an account. Unfortunately, some such schemescan be vulnerable to data-mining (e.g., asking for a mother's maidenname or county in which the user owns property, both of which can beobtained from public records). Other schemes can be vulnerable toguessing (e.g., requiring the user to supply answers to a series ofquestions at enrollment time such as “what is the name of your pet?” forwhich there are common responses). If questions attempting to elicitless common responses are used (e.g., “what is the name of your gradeschool teacher?”) a risk exists that a legitimate user will, in additionto forgetting the password, also forget the information needed tocomplete a password reset action. Other schemes, such as requiring thatthe user call a help desk for assistance can be expensive, and can alsobe subject to social engineering on the part of an attacker. If the usermaintains a personal website or makes use of social networking sites, anattacker potentially has even more information to mine (e.g., for petnames, names of friends, former addresses etc.) and thus may have aneven easier time gaining unauthorized access to the legitimate user'saccount.

As described in more detail below, using the techniques disclosedherein, a series of preferences, such as whether an individual likesonions and whether an individual listens to reggae music are used tohelp determine whether a request has been submitted by a legitimate useror by an attacker. In various embodiments, additional information isused to augment the preference information supplied by the user. Thetechniques described herein can be used as a secondary form ofauthentication (e.g., for when the user has forgotten or is otherwiseunable to supply an existing password) and can also be used as a primaryform of authentication (e.g., instead of a traditional password, PIN, orother credential), as applicable.

FIG. 1 illustrates an embodiment of an environment in whichauthentication is provided. In the example shown, a user (hereinafterreferred to as “Alice”) maintains several bank accounts with Acme Bank.Alice banks with Acme Bank, both at typical branch offices, and alsoonline, by visiting Acme Bank's website 112. Alice connects to website112 using her laptop 114 and on occasion also uses her mobile phone 116to perform tasks such as checking her account balances. In variousembodiments, other types of clients (not shown) are used to communicatewith website 112, such as personal digital assistants, set-top boxes,game consoles, etc. In addition to (and/or instead of) websites, such aswebsite 112, the techniques described herein may also be used inconjunction with other electronic environments, such as those providingauthentication to intranet services, network appliances, game servers,etc.

The first time Alice decides to avail herself of Acme Bank's onlinebanking features, she visits website 112 and commences an enrollmentprocess. She is asked to choose a username and supply information suchas her full name, phone number, and bank account numbers. She is alsoasked to select a password. As described in more detail below, she isalso asked to provide additional information (e.g., her preferences forassorted things) for use in the event she ever forgets her password oris otherwise unable to authenticate herself using her selected password.

In the example shown in FIG. 1, authentication module 104 is configuredto capture information at the time of Alice's enrollment and store thatinformation in database 106, for example, as a set of preferences 108associated with Alice. Database 106 also stores other information, suchas policies 110 to be used by authentication module 104 when determiningwhether to grant Alice access to banking resources on subsequent visitsand/or when determining whether Alice should be permitted to reset orrecover her password in the event that she later forgets it. Other datastructures may also be used to store preferences 108 and/or policies 110as applicable.

System 102 provides authentication services for website 112. System 102also provided authentication services for Acme's bank by phone tool 120,which allows customers to check their account balances and perform otheractions via conventional telephone 118. In various embodiments, system102 and website 112 are maintained by two different entities. Forexample, a website hosting company might maintain website 112 under acontract with Acme Bank, while another entity maintains authenticationsystem 102. Similarly, when Alice visits website 112, a portion of thecontent rendered in her browser may be served by the web hostingcompany, while another portion of the content (120) may be served bysystem 102.

In various embodiments, the infrastructure provided by portions ofauthentication system 102 is located on and/or replicated across aplurality of servers rather than the entirety of authentication system102 being collocated on a single platform. Such may be the case, forexample, if the contents of database 106 are vast and/or if system 102is used to provide authentication services to multiple websites 112and/or other electronic resources not shown. Similarly, in someembodiments the serving of content such as website 112 is provided bysystem 102, rather than being provided by a separate system (e.g.,provided by a web hosting company). Whenever authentication system 102performs a task (such as receiving information from a user,authenticating the user, etc.), either a single component or a subset ofcomponents or all components of authentication system 102 may cooperateto perform the task.

FIG. 2 is a flow chart illustrating an embodiment of an enrollmentprocess. In various embodiments, the process shown in FIG. 2 isperformed by system 102. The process begins at 202 when a list of things(e.g., such as food items and styles of music) is provided to a user. At204, preference information associated with at least some of the thingsis received from the user. At 206, preference information associatedwith the user is stored. In some embodiments portions of the processshown in FIG. 2 are repeated. For example, items may be provided to auser in batches, and corresponding batches of preference information arereceived and stored as appropriate. In some embodiments, batches ofpreference information are received/stored in conjunction with a laterauthentication attempt, when the user has gained access to his or heraccount, and/or when the user otherwise lets his or her preferences beknown to the system.

FIG. 3A illustrates an embodiment of an interface for capturingpreference information. In some embodiments the interface shown in FIG.3A is used in conjunction with the process shown in FIG. 2. Items 302are presented to a user (e.g., at 202), such as Alice, at enrollmenttime, such as via website 112. Alice indicates her preferences (if any)for each item by selecting the checkbox that corresponds to herpreference. In some embodiments a default preference of “not sure” or“no opinion” is checked. While in the example shown in FIG. 3A a totalof 120 questions are shown as being presented, in various embodimentsmore, fewer, and/or a variable and/or dynamically and/or randomlydetermined number of questions are presented at enrollment, depending onsuch factors as the degree of certainty and/or security required, thenature and/or value of the resource(s) being protected, the quality,reliability, etc. of the particular questions presented, etc.

In the example shown in FIG. 3A, Alice has indicated that she likescats, that she does not like anchovies, and that she is unsure ofwhether she likes playing golf. After making all of her selections,Alice submits her preferences to system 102 (e.g., at 204). System 102stores Alice's preferences, e.g., in database 108 for later use.

Item 304 (“have you been to Chicago?”) is an example of a life question,included in some embodiments to augment the preference informationcollected from the user, and described in more detail below.

FIG. 3B illustrates an embodiment of an interface for capturingpreference information. In some embodiments the interface shown in FIG.3B is used in conjunction with the process shown in FIG. 2. As usedherein, preference information for a thing includes information thatdescribes how a particular user feels about that thing. Preferenceinformation can be positive (e.g., “I like cats”), negative (e.g., “Idon't like anchovies”), and neutral (e.g., “I don't know if I likeplaying golf”). In some embodiments a Likert scale is used to collectand preference information. For example, in the interface shown in FIG.3B, instead of answering yes or no questions, users are requested torate their preferences for items on a five point scale, with 1indicating a strong dislike, 3 indicating a neutral opinion, and 5indicating a strong like of an item. Other expressions of preferences,such as expressions of habit, can also be input in a similar manner.

FIG. 3C illustrates an embodiment of an interface for capturingpreference information. In some embodiments the interface shown in FIG.3C is used in conjunction with a portion of the process shown in FIG. 2.In the example shown, rather than providing users with items, users areasked to supply their own list of items and corresponding preferences.Portion 202 of the process shown in FIG. 2 is omitted accordingly.

FIG. 4 illustrates an embodiment of an interface for capturingpreference information. In some embodiments the interface shown in FIG.4 is used in conjunction with the process shown in FIG. 2. In theexample shown, users are asked to select a category 402. Items belongingto the selected category are then displayed to the user in region 404.Users are requested to select a total of eight liked items and eightdisliked items from region 404, and are permitted to switch betweencategories 402 (causing different items to be displayed in region 404)to arrive at a total of 16 preferences for 16 items. Typically, mostusers are neutral about most topics. By using the interface shown inFIG. 4, users can avoid having to repeatedly mark items as “no opinion.”

It is typically easier for people to remember preferences (e.g., “I likemushrooms”) than arbitrary information such as a password. Additionally,one typical goal of service providers is to permit legitimate users tocorrectly answer authenticating information while at the same timemaking it unlikely for illegitimate users to correctly do so. In someembodiments the items for which a user's preference is solicited(especially in the aggregate) have a “high entropy,” meaning that givena random sample of individuals, it would be difficult to guess aparticular individual's preference for a particular item, whetherstatistically, or based on knowledge of basic demographic or otherinformation about an individual that can readily be obtained (e.g.,through data-mining of publicly available information). Examples ofitems with low entropy in their corresponding user preferences includeitems such as “vacation” and “money” as likes and “being sick” and“pain” as dislikes. Conversely, “seafood,” “going to the opera,” and“horror movies” are examples of items with high entropy in theircorresponding user preferences.

The following are examples of items for which a given user's areunlikely to be guessed by a third party, but are also likely to beremembered by that user.

In the “TV” category, users may select among different types of showssuch as: reality shows, news, sports, sitcoms, dramas, movies, soapoperas, game shows, and documentaries.

In the “food” category, users may select among different types of foodsuch as: American, Barbecue, Cajun/Southern, California-Fusion,Caribbean/Cuban, Chinese/Dim Sum, Continental, Deli, Eastern-European,Fast Food/Pizza, French, German, Indian, Italian, Japanese/Sushi,Jewish/Kosher, Korean, Mediterranean, Mexican, Middle Eastern, Seafood,Soul Food, South American, Southwestern, Spanish, Thai,Vegetarian/Organic, Vegan, Vietnamese.

In the “Music” category, users may select among different styles ofmusic such as: Acoustic, Alternative, Big Band/Swing, Blues, Christian &Gospel, Classic Rock n' Roll, Classical, Country, Dance/Electronica,Disco, Easy Listening, Folk, Hard Rock & Metal, Indie, Instrumental,Jazz, Latin, Modern Rock n' Roll, New Age, Oldies, Opera, Pop/Top 40,Punk, Rap/Hip Hop, Reggae, Show tunes, Soul/R&B, Soundtracks, WorldMusic/Ethnic.

In the “Places” and “Activities” categories, users may select amonggoing to different types of places/events: Amusement Parks, AntiqueStores, Art Galleries, Bars/Nightclubs, Beach, Bookstores, CharityEvents, Circuit Parties, Coffee Houses, Comedy Clubs, Concerts, DanceClubs, Flea Markets, Garage Sales, Karaoke/Sing-along, Libraries, LiveTheater, Movies, Museums, Opera, Parks, Political Events, Raves/Parties,Restaurants, Shopping Malls, Skate/Bike Parks, Sporting Events,Symphony, Volunteer Events.

In the “Sports” category, users may select among different types ofactivities: Aerobics, Auto racing/Motocross, Baseball, Basketball,Billiards/Pool, Cycling, Dancing, Football, Golf, Hockey, Inlineskating, Martial arts, Running, Skiing, Soccer, Swimming, Tennis/Racquetsports, Volleyball. Walking/Hiking, Weights/Machines, Yoga.

The aforementioned categories and items are examples of things for whicha user's preference can be sought. In some cases, some preferences(e.g., “I like Italian food” and “I don't like onions”) are observable,such as by family members and coworkers. Some “likes” can also leavetraces (e.g., a record of a purchase of a CD of a given type). However,“dislikes” are typically less likely to leave traces that can be mined.Additionally, very few third parties will be able to observe a specificindividual's preferences for items across multiple categories. Forexample, while a co-worker might observe Alice's preference for Italianfood, the co-worker is less likely to know that Alice likes visitingcomedy clubs, dislikes Karaoke, and reads romance novels (or all of thatinformation collectively). In various embodiments, the number of likesand dislikes that a user such as Alice must supply, and from how manydifferent categories the preferred items are selected is configurable(e.g., by an administrator, based on one or more policies).

Additional formats may also be used to collect preference information.For example, rather than soliciting an answer of “like,” “dislike,” or“no opinion,” in some embodiments the user is asked to perform aselection of more and less important events. For example, the followingquestion is of that type: “Among the following sports, which one(s) doyou prefer watching: auto racing, baseball, basketball, bowling,cricket, football, golf, hockey, soccer, ski jump, figure skating,tennis.” A similar question can be posed to ask which ones the user doesnot like watching.

Yet another example of a technique for collecting user preferences is toprovide a question that permits several simultaneous correct entries.For example, “Describe your personality by selecting one or moresuitable descriptions: introvert, extrovert, peaceful, worrying,goal-oriented, impulsive, confrontational, shy, passionate.” In thisexample, some of the pairs are in contradiction to each other, such as“introvert” and “extrovert,” while others are roughly synonymous, suchas “introvert” and “shy.”

In addition to soliciting a user's preference for things, as previouslymentioned system 102 can be configured to solicit other kinds ofinformation about the user's life that are neither readily availablethrough data mining, nor easily guessable. Examples include “do yousleep on the left side of the bed,” “have you been to Chicago,” “do yousnore,” etc. Different types of questions can also be mixed within aninterface. For example, Alice may be asked to rate some items on a scaleof 1-5, to select 4 likes and dislikes using an interface as is shown inFIG. 4, and may be presented with a list of life questions to beanswered using a set of radio buttons at 202 in the process shown inFIG. 2.

Preferences can be captured (and later tested against) in a variety ofways. For example, in addition to answering written questions viawebsite 112, preferences could also be captured acoustically (e.g., overthe phone, via a series of voice prompts to which the user responds witha spoken “yes” or “no”). Similarly, the user could be played a set ofaudio clips and asked whether they like or dislike the sample. Othernon-text entry methods can also be used, as applicable, such as devicesused by the physically disabled.

FIG. 5 is a flow chart illustrating an embodiment of an authenticationprocess. In various embodiments, the process shown in FIG. 5 isperformed by system 102. The process begins at 502 when preference datais received, such as from a user. The received preference data isreceived either as a selection of items (e.g., by the user havingselected radio buttons, checkboxes, etc.), as a classification of items(e.g., by indicating a preference for a presented item on a slidingscale, a preference for one item over another, a ranking of presenteditems, etc.), or a combination thereof (collectively referred to hereinas a “selection” of preference data). At 504, the received preferencedata is compared to stored preference data. At 506 it is determinedwhether an action should be authorized based at least in part on thecomparison.

FIG. 6 illustrates an embodiment of an interface for authenticating auser. In some embodiments the interface shown in FIG. 6 is used inconjunction with the process shown in FIG. 6. Suppose Alice, afterregistering with website 112 (and providing preference information viathe interface shown in FIG. 4) stops using online banking for a periodof time. She eventually forgets her password. To resume using thefeatures of website 112, Alice must reset her password. Alice visitswebsite 112 and selects an “I forgot my password” option from theappropriate location on the site. Alice is then presented with interface600. In the example shown, Alice is requested to provide preferenceinformation for each of the items shown in interface 600. Afterselecting the appropriate radio buttons, she clicks “done” and thepreference information is submitted to system 102 (502), If Alice makesa mistake, she can “reset” the radio buttons as needed. The items shownin interface 600 need not exactly correspond to the items for whichAlice previously provided preference information. For example, if Aliceused the interface shown in FIG. 3A to enroll her preferences, only asubset of the items might be shown in interface 600. What percentage ofitems to show in interface 600 (and what mix of likes, dislikes, whetherneutral items should be included, etc.) is customizable, e.g., based onpolicies specified by an administrator.

In some cases, a designated portion of the items shown in FIG. 6 arenew. For example, Alice may have provided preference information for 75%of the items shown in interface 600. Her responses to those items willbe used in the authentication process. The remaining 25% of questionsmay be used to augment Alice's existing preference information (e.g., bylearning new information about Alice), may be used to test the entropyof questions for future use, and/or may be used for other purposes. Byadding new questions and by providing only a portion of all registeredquestions, an attacker may have a more difficult time guessing whichquestions are associated with Alice, and have a harder time attemptingto obtain the correct answers to the questions to be asked in a futureauthentication session.

Comparing Received Preferences to Stored Preferences

A variety of techniques can be used to store and subsequently comparestored preferences (e.g., those received from Alice at enrollment) tosubsequently received preferences (e.g., received through interface600). For example, suppose system 102 makes use of the interface shownin FIG. 3A. In that scenario, system 102 makes use of a total of 120different things (also referred to herein as “questions”), notatedindividually as q_(i), where i is a value from 1 to 120. Each questionq_(i) can be associated with a directed graph g_(i) with d_(i) vertices.If there is a directed edge from vertex v_(ij) to vertex v_(ik), then anentry w_(ijk) in an adjacency matrix A associated with the graph is setto a pre-set value y_(ijk); if there is no such edge then the associatedentry is set at a value T (e.g., negative infinity).

During the process shown in FIG. 2, the user is requested to answer eachquestion q_(i). An answer corresponds to selection of one or more of thevertices associated with this question. A selected vertex is associatedwith the value 1, while a vertex that is not selected is associated withthe value 0. A variable u_(ij) is used to record these values—u_(ij) isset to 1 (resp. 0) if the vertex v_(ij) is (resp. is not) selected inthis process. The value U, which is specific to the given user, consistsof the entire list of recorded values u_(ij) for this user. The value Uis stored by system 102. If the user doesn't answer certain questions(and/or has “no opinion”), such questions can be thought of as questionsfor which none of the vertices are selected.

In some embodiments, the preferences supplied at 204 in the processshown in FIG. 2 are evaluated to determine whether the enrollment issuccessful. For example, if the user answers all questions “yes,” allquestions “no,” or leaves all questions as “no opinion,” a problem maybe indicated. One way of determining whether an enrollment attemptshould be deemed successful is as follows. The sum of all(w_(ijj)*u_(jj)) is computed, for 0<i, j<n+1, where n is the number ofquestions (e.g., 120). This sum is denoted S1. If S1 is greater thansome pre-set threshold value t1, then enrollment is consideredsuccessful, otherwise not. If the enrollment is not consideredsuccessful, then the value U is erased, and the user has to start over.

When an authentication is attempted (e.g., when Alice wishes to resether password), system 102 retrieves the associated value U. Then, theuser is requested to answer questions q_(i). An answer (502) correspondsto selection of one or more of the vertices associated with thisquestion. A selected vertex is associated with the value 1, while avertex that is not selected is associated with the value 0. A variablez_(ij) is used to record these values; thus, z_(ij) is set to 1 (resp.0) if the vertex vi is (resp. is not) selected in this process.

To determine whether a given authentication attempt should be consideredsuccessful, the following is performed at 504: The sum of all(w_(ijk)*u_(ij)*z_(ik)) is computed, for 0<i, j, k<n+1. This sum isdenoted S2. At 506, it is determined whether S2 is greater than somepre-set threshold value t2. If so, authentication is consideredsuccessful, otherwise not.

The value y_(ijk) is the “benefit” of selecting outcome j for question iduring enrollment, and then subsequently selecting outcome k forquestion k during authentication. A low value, such as the value T, canbe used as a “punishment” for answering a question incorrectly, whereasa higher value is to be interpreted as a reward for answering thequestion correctly.

Numerical Example

Suppose q1=“Do you like cats?” with three possible answers “yes”,“neutral,” and “no.” These possible answers correspond to three nodesv₁₁, v₁₂, and v₁₃. All values u₁₁, u₁₂, and u₁₃ are set to 0. If theuser selects that he likes cats, then the value u₁₁ is set to 1; if hehas no strong opinion, then u₁₂ is set to 1; and if he does not likecats, u₁₃ is set to 1.

Additional constraint values are y₁₁₁=3, y₁₁₂=−5, y₁₁₃=T, y₁₂₁=0,y₁₂₂=0, y₁₂₃=0, y₁₃₁=T, y₁₃₂=−6, and y₁₃₃=4.

When the user attempts to authenticate, the values z₁₁, z₁₂, and z₁₃ areset. The nine combinations of preferences during enrollment vs.authentication are as follows:

(LIKE, LIKE): S2=y₁₁₁=3

(LIKE, NO OPINION): S2=y₁₁₂=−5

(LIKE, DISLIKE): S2=y₁₁₃=T

(NO OPINION, LIKE): S2=y₁₂₁=0

(NO OPINION, NO OPINION): S2=y₁₂₂=0

(NO OPINION, DISLIKE): S2=y₁₂₃=0

(DISLIKE, LIKE): S2=y₁₃₁=T

(DISLIKE, NO OPINION): S2=y₁₃₂=−6

(DISLIKE, DISLIKE): S2=y₁₃₃=4

Thus, if the user first says he likes cats (during enrollment), andlater says he does not during authentication, then the sum S2 becomesminus infinity. The same thing happens if he says that he dislikes catsduring enrollment, and later says he likes them. (In variousembodiments, the punishment is set to a value of much smaller absolutevalue. For example, while a correct answer may give 5 points, anincorrect answer may cause the loss of 20 points.) However, if he has noopinion during enrollment, then his answer during authentication alwaysresults in the sum S2=0. If he has an opinion during enrollment, and nostrong opinion during authentication, the sum is set to a small negativevalue. If the user retains his like or dislike from enrollment toauthentication, S2 is a positive number.

The assignment of low absolute weights allows for the later cancellationof incorrect answers to questions that the user has no strong opinion of(e.g., the types of questions where temporal variance is going to be thegreatest). The assignment of large negative weights introduce strongnegative feedback for questions where users have a strong opinion, butwhere the answer during authentication is incorrect. The assignment ofpositive weights allow for the detection of correct answers given duringauthentication. The assignment of low absolute weights reduces theimpact of a small number of incorrect answers during authentication,where the incorrect answers are not contradictory with the userspreviously stated opinion, but merely not in complete agreement withthese.

As multiple questions are considered, the sum S2 corresponds to thecumulative value of all these contributions from the differentquestions. A sum that is greater than the set threshold t2 means thatthe user answered in a similar-enough manner during authentication as hedid during enrollment. In some embodiments if the sum is not greaterthan this threshold, then the user either mistook a strong like for astrong dislike (which is unlikely) or vice versa; stated that he had nostrong opinion in the authentication phase for a sufficient number ofquestions he stated a strong opinion for in the enrollment phase, or acombination. The threshold t2 of the authentication phase, and thevalues y_(ijk) are set in a manner that balances the risk for falsepositives with the risk for false negatives, and reflects the degree towhich the answers to these questions are estimated to be maintained overtime in some embodiments. The threshold t1 of the enrollment phase isset to guarantee a sufficient number of answers that are not “no strongopinion,” in turn making it impossible to authenticate by answering “noopinion” to all or too many questions. In some embodiments, severalvalues t2 are used (e.g., one for each type of access right), out ofsome collection of possible values and types of account access andprivileges. The value t2 can be a function of the value t1, and of someminimum value required for access, as well as of other parametersdescribing the user and his or her risk profile.

Questions with more than three possible answers, such as degrees ofopinion, and questions that have only two possible answers, and any typeof question with multiple answers can be scored by adapting thetechniques described herein.

In some embodiments instead of assigning the variable y_(ijk) anarbitrary value describing the associated reward or punishment, a set ofvalues representing y_(ijk) can be selected and saved. Each such valuewill be a point in a two-dimensional space, with an x-coordinate and ay-coordinate. For practical purposes, we will assume that all thex-coordinates are distinct, and that all coordinates are represented byinteger values in a given range from 0 to p, where p is a systemparameter. Associated with each user is a random polynomial f(x)described with random integer parameters in the same range, 0 to p, andwhere the polynomial is evaluated modulo p.

For an instance y_(ijk) with a large positive value, a large number ofpoints on the curve f(x) are selected and associated with the indices iand k; for a large negative value, a small number of such points areselected; and for a value y_(ijk) inbetween, an intermediary number ofsuch points are selected. The exact mapping between values of y_(ijk)and the number of selected points on the curve f(x) is a systemparameter that can be customized to minimize false positives and falsenegatives. The variable R_(ik) is used to denote the collection ofpoints associated with y_(ijk), where a large number of points from f(x)is selected if y_(ijk) is large, and a smaller number of points fromf(x) are selected if y_(ijk) is small. Once a number of points on f(x)has been selected, these are stored in the record R_(ik), along withrandom points on a random polynomial f′(x) to fill up those positionsthat do not contain f(x) values, up to a given maximum number of valuesthat is a system parameter. Here, f′(x) has the same or larger degreethan f(x), or corresponds to a random selection of points from theappropriate space. If for each value y_(ijk) ten points in R_(ik) arestored, then a high y_(ijk) value could be represented by ten pointsfrom f(x); a value y_(ijk) close to zero could be represented by eightvalues from f(x) and two values from f′(x); and the value T could berepresented by ten values from f′(x). The ordering of values from f(x)and f′(x) as they are stored in R_(ik) would be random or pseudo-random,and not disclosed.

Each value y_(ijk) would be represented in this manner. The matrix ofall values R_(ik) would be saved. This takes the place of the previouslydefined value U.

In the above example, the degree of the polynomial f(x) may be chosen asn*10−1. This means that, for reconstruction of the polynomial f(x) fromrecorded points, it is necessary to know n*10 points on the curve. Thedegree of f(x) could, more generally, be chosen as n*L−1−d, where L isthe number of points stored per record R_(ik), and d is an integer valueregulating the balance between false positives and false negatives, andcorresponds to the total number of values from f′(x) that can beselected as all questions are answered, while still passing theauthentication phase.

During the authentication phase, the user selects answers. For each suchanswer, he selects an associated collection of points, in turnassociated with the values i (of the question) and k (of the response tothe question). During authentication, the machine used by the user doesnot know what elements are from f(x) and what elements are from f′(x).However, if a selection is made for which R_(ik) has a large portion ofvalues from f′(x), then it is unlikely that only points from f(x) aregoing to be selected, and therefore, unlikely that the polynomial f(x)can be reconstructed. If there is a failure, the machine can try anotherset of points corresponding to the same user selection. A large numberof these can be tried. If more than a certain number, say 1000, aretried, then the login script can generate an error to the user andrequest that the user attempts to authenticate again. An attacker wouldnot have to limit himself to 1000 attempts, but if he has a large numberof incorrect selections, he is unlikely to ever be able to reconstructthe polynomial. A machine can determine whether a polynomial iscorrectly interpolated by trying to compute f(x) on an input value xgiven by the server. If this is done correctly, then the server willallow the client access, and call the authentication attempt successful.The machines would not have to communicate the values in the clear, butcould do this over an encrypted channel, or the client machine may senda one-way function of the result f(x) for the requested value x. Sincethe server knows the polynomial f(x) as well as x, it can verify whetherthis is a correct value. It is also possible to use an f-value for aknown x-coordinate, such as x=0, as a cryptographic key, provided thispoint on the curve is never chosen to be part of an entry R_(jk). Thus,a user that answers a sufficient number of questions correctly wouldenable his computer to compute f(0) using standard interpolationtechniques (and as described above), thereby deriving the key f(0); acomputer that fails to compute f(0) would not be able to perform theassociated cryptographic actions. Thus, users who fail to authenticatesufficiently well would cause their computer to be unable to performsuch actions.

In various embodiments other techniques are used to score stored (andsubsequently received) preferences. For example, the entropy of aparticular question can be used as a weight that is used when computingS2. Thus, a question such as “do you sleep on the left side of the bed”may be inherently worth more points (based on its entropy) than aquestion such as “do you like ice cream.” Special rules can also takeinto account answers—particularly to life questions—that wrong answer towhich may cause an authentication attempt to fail irrespective of theother questions being answered correctly. For example, if Aliceindicates that she has been to Chicago at enrollment, and thensubsequently denies being there, such an event might indicate that anattacker is trying to impersonate Alice. Conversely, mechanisms can alsobe used to make sure that for questions the answers to which mightevolve over time (e.g., fondness for certain foods considered to appealonly to adults, such as mushrooms and sushi) don't result in falsenegatives.

Policies

A variety of policies can be put in place based on the security andother needs of website 112 (or other appropriate electronic entity). Forexample, different users may have different personal thresholds for whatwill constitute a valid authentication and what will not, but certainglobal minimums can be applied simultaneously. Additionally, differentactions can be taken based on factors such as by how much a thresholdwas exceeded. For example, in a banking context, several thresholdscould be used in which if the highest threshold is exceeded, the user ispermitted full access to his or her account. If the second highestthreshold is exceeded, the user is permitted full access to the account,but a flag is set alerting an administrator to review the user's accountonce the user logs off. Other lower thresholds can also be set withtheir own corresponding set of permitted actions, such as allowing theuser read-only access to the account, informing the user that accesswill only be granted after any additional step is performed (e.g.,requiring the user to make or receive a phone call, a respond to a pieceof email, etc.).

Policies can also be used to specify, e.g., how many likes/dislikes auser must supply, whether (e.g., in the case of the interface shown inFIG. 4) items from multiple categories must be selected, and if so, fromhow many categories. If a large pool of items are available for users toindicate preferences for, in some embodiments the selection of whichitems a user is asked to provide prefaces for is randomized and/or theinterface used for authentication is randomized. Policies can also beused to specify whether—if only one or two questions are answeredincorrectly during authentication—the stored preference informationshould be updated to reflect the discrepancy. For example, in someembodiments if a user indicates a liking for a single food that was notpreviously liked, and does so multiple times, the preference informationfor that item for that user will be updated automatically to reflect theuser's new preference. In various embodiments users, upon successfulauthentication, can initiate an “update” process in which they arepermitted to repeat the process shown in FIG. 2 to update preferences.

Additional information, such as the presence or absence of a cookie, canbe use to adjust thresholds (and permitted actions/levels of access)accordingly. As another example, suppose Alice's phone 116 includes aGPS. In some embodiments a side channel may be used to capture Alice'slocation information and to present Alice (e.g. in interface 600) with aquestion that asks if she was in <location> last week. Alice's GPScoordinates can also be used to determine the selection of the thresholdrequired to pass authentication: a person attempting to authenticatefrom a location close to Alice's believed location (e.g., her homeaddress, places she frequents, etc.) may be offered a lower thresholdthan a person who is distant from all likely GPS positions of Alice. Insome embodiments, multiple types of additional information areused/combined. For example, if Alice's GPS reports that she is currentlyin California, but her alleged IP address reflects that she is inRomania, the threshold score needed to gain access to her account may beincreased, she may be required to supply a username and password, andalso provide preferences whereas she might otherwise only be required tosupply a correct username/password, etc.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, the invention is not limitedto the details provided. There are many alternative ways of implementingthe invention. The disclosed embodiments are illustrative and notrestrictive.

What is claimed is:
 1. A system, comprising: an authentication moduleconfigured to, using a set of one or more processors: present at leastone item to a user via one or more interfaces, wherein the user isprompted to classify the at least one item at least in part byselecting, from a set of selectable preferences, a preference for the atleast one item, and wherein the set of selectable preferences comprisestwo or more of a positive preference, a negative preference, and aneutral preference; receive, from the user, a classification of the atleast one item, wherein the classification comprises a selection ofpreference, from the set of selectable preferences, for the at least oneitem; compare, to a stored classification associated with the user, thereceived classification comprising the selection of preference for theat least one item; and determine that an action should be authorizedbased at least in part on the comparison between the storedclassification associated with the user and the received classificationcomprising the selection of preference for the at least one item; and amemory coupled to the set of one or more processors and configured toprovide the set of one or more processors with instructions.
 2. Thesystem of claim 1 wherein the action includes a password reset request.3. The system of claim 1 wherein the action includes receiving access toa service.
 4. The system of claim 1 wherein the one or more interfacesincludes a graphical user interface.
 5. The system of claim 1 whereinthe one or more interfaces are configured to obtain the classificationacoustically.
 6. The system of claim 1 wherein the receivedclassification and the stored classification are of different types. 7.The system of claim 1 wherein determining that the action should beauthorized includes computing a score based at least in part on thecomparison and determining whether the score exceeds a threshold.
 8. Thesystem of claim 7 wherein the threshold is determined based at least inpart on an entropy score.
 9. The system of claim 1 further comprising anenrollment interface configured to capture a plurality ofclassifications.
 10. The system of claim 9 wherein the enrollmentinterface is configured to display a plurality of categories.
 11. Thesystem of claim 9 wherein the enrollment interface is configured toreceive a selection of a category and in response display an itemassociated with the category.
 12. The system of claim 11 wherein theenrollment interface is configured to capture a classification of theitem associated with the selected category.
 13. The system of claim 9wherein the enrollment interface is further configured to provide anaudio sample.
 14. The system of claim 1 wherein the receivedclassification includes a classification of at least one of a food, anactivity, a television show, and a style of music.
 15. The system ofclaim 14 wherein the received classification comprises an indication ofa negative preference for the at least one item, and wherein theauthentication module is configured to determine that an action shouldbe authorized based at least in part on the comparison between thestored classification associated with the user and the receivedclassification comprising the indication of the negative preference forthe at least one item.
 16. The system of claim 14 wherein the receivedclassification comprises an indication of a neutral preference for theat least one item, and wherein the authentication module is configuredto determine that an action should be authorized based at least in parton the comparison between the stored classification associated with theuser and the received classification comprising the indication of theneutral preference for the at least one item.
 17. A method, comprising:presenting at least one item to a user via one or more interfaces,wherein the user is prompted to classify the at least one item at leastin part by selecting, from a set of selectable preferences, a preferencefor the at least one item, and wherein the set of selectable preferencescomprises two or more of a positive preference, a negative preference,and a neutral preference; receiving, from the user, a classification ofthe at least one item, wherein the classification comprises a selectionof preference, from the set of selectable preferences, for the at leastone item; comparing, to a stored classification associated with the userand using an authentication module and a set of one or more processors,the received classification comprising the selection of preference forthe at least on item; and determining, using the authentication moduleand the set of one or more processors, that an action should beauthorized based at least in part on the comparison between the storedclassification associated with the user and the received classificationcomprising the selection of preference for the at least one item. 18.The method of claim 17 wherein the action includes a password resetrequest.
 19. The method of claim 17 further comprising capturing, via anenrollment interface, the stored classification during an enrollment.20. A computer program product embodied in a tangible non-transitorycomputer readable storage medium and comprising computer instructionsfor: presenting at least one item to a user via one or more interfaces,wherein the user is prompted to classify the at least one item at leastin part by selecting, from a set of selectable preferences, a preferencefor the at least one item, and wherein the set of selectable preferencescomprises two or more of a positive preference, a negative preference,and a neutral preference; receiving, from the user, a classification ofthe at least one item, wherein the classification comprises a selectionof preference, from the set of selectable preferences, for the at leastone item; comparing, to a stored classification associated with the userand using an authentication module and a set of one or more processors,the received classification comprising the selection of preference forthe at least one item; and determining, using the authentication moduleand the set of one or more processors, that an action should beauthorized based at least in part on the comparison between the storedclassification associated with the user and the received classificationcomprising the selection of preference for the at least one item. 21.The system of claim 1, wherein a plurality of items are presented to theuser, and wherein the user is prompted to classify each of the pluralityof items at least in part by making, for a given item, a correspondingselection of preference from a corresponding set of selectablepreferences.
 22. The system of claim 1, wherein the set of selectablepreferences comprises the positive preference, the negative preference,and the neutral preference.
 23. The system of claim 1, wherein eachselectable preference in the set of selectable preferences is renderedin the one or more interfaces, and wherein the selection of preferencecomprises a user input with respect to a rendered selectable preference.24. A system, comprising: an authentication module configured to, usinga set of one or more processors: present one or more items to a user viaone or more interfaces, wherein the one or more items comprise at leastone of a food, an activity, a television show, and a style of music;receive, from the user, a classification of a presented item, whereinthe classification comprises an indication of a negative preference forthe presented item; compare, to a stored classification associated withthe user, the received classification comprising the indication of thenegative preference for the presented item; and determine that an actionshould be authorized based at least in part on the comparison betweenthe stored classification associated with the user and the receivedclassification comprising the indication of the negative preference forthe presented item; and a memory coupled to the set of one or moreprocessors and configured to provide the set of one or more processorswith instructions.
 25. A system, comprising: an authentication moduleconfigured to, using a set of one or more processors: present one ormore items to a user via one or more interfaces, wherein the one or moreitems comprise at least one of a food, an activity, a television show,and a style of music; receive, from the user, a classification of apresented item, wherein the classification comprises an indication of aneutral preference for the presented item; compare, to a storedclassification associated with the user, the received classificationcomprising the indication of the neutral preference for the presenteditem; and determine that an action should be authorized based at leastin part on the comparison between the stored classification associatedwith the user and the received classification comprising the indicationof the neutral preference for the presented item; and a memory coupledto the set of one or more processors and configured to provide the setof one or more processors with instructions.